1. Field of the Invention
The present invention is directed to a fiber optic catheter, and more particularly to a fiber optic catheter with a twistable tip. The tip can be twisted remotely by rotating the proximal end of a torquing means internal to the catheter. The torquing means may be a torque wire or a guide wire lumen attached to the catheter at or near the distal end.
2. Description Of the Prior Art
Fiber optic catheter assemblies have increasingly been used for probing and clearing obstructions in various vessels such as arteries. The size of the vessel and the distance from the insertion point to the critical region in the vessel determine the characteristics of the catheter to be used. For example, in some situations it is desirable to insert a very thin catheter a considerable distance into a vessel. The catheter must be quite flexible so that it may be steered considerable distances through winding vessel passages.
Once the tip of the catheter reaches the critical point of the vessel passage, it is often desirable to have the tip oriented in a particular direction. It would be ideal if the tip self aligned with the obstruction, however often the tip must be further positioned to carry out an operation. The diameter of the optical fibers in fiber optic catheters is quite small and it is often necessary to continuously move and retarget the optical beam emanating from the optical fibers to ablate a large obstruction. Because the optical fibers are not independently directable inside the catheter, the entire end of the catheter containing the mounted optical fiber must be moved. This problem is addressed by Wells U.S. Pat. No. 4,844,062. The Wells patent discloses an eccentric catheter having optical fibers located off the axial center of the catheter. When the catheter is rotated, the beam from the optical fiber sweeps out a path larger than the diameter of the beam.
A catheter used to traverse considerable distances through a complex anatomy must be flexible. Commonly, the torque to rotate the tip is transmitted through the flexible outer jacket of the catheter. However, the torque applied at the proximal end of the catheter often will not be transferred to the distal end to rotate the tip. Instead the catheter will likely twist and kink under the torsional load. The friction between the catheter and its surroundings over the length of the catheter in a complex anatomy is substantial and the flexible catheter does not have enough torsional rigidity to overcome the friction and transmit torque from its proximal end to its distal end.
One solution to this problem is to increase the stiffness of the catheter wall. This solution has the disadvantage of decreasing the steerability and the ease of insertion of the catheter into a winding passage. This solution is thus limited to short distance and direct insertions.
Flexible catheters do not have sufficient torsional stiffness to be twisted and rigid catheters do not have sufficient flexibility to be inserted into a complex passage. Ideally a catheter should be flexible to permit adequate insertion and steerability while being able to transmit sufficient torque to twist the tip. Additionally the catheter should self align with the obstruction so that a minimum of remote intervention is required. The known art does not disclose any device to self align the tip of a catheter inserted in a complex anatomy. Clark et al. U.S. Pat. No. 5,114,403 discloses a catheter torque mechanism having a torque wire attached to the tip of a catheter and attached to a rotation control mechanism. Clark does not disclose attaching the torque wire to specific points near the catheter tip to achieve specific torque performance, nor does Clark teach altering the material or dimensions of the torque wire to achieve the torque and flexibility profile necessary to be effective in a complex anatomy.
Mueller, Jr., U.S. Pat. No. 4,775,371 discloses a stiffened dilation catheter having a catheter with a section made from material being stiffer or having thicker proximal walls at a distal section of the catheter.
Sampson et al. U.S. Pat. Nos. 4,573,470 and 4,641,654 disclose steerable catheters having a rotatable guide wire. However, the guide wire does not impart any rotation or torque to the tip of the catheter. Gould et al. U.S. Pat. No. 5,055,109 and Gaiser et al. U.S. Pat. No. 4,998,917 disclose steerable catheters with torque transmitting assemblies. However, these inventions disclose deflecting the tip so that it is steerable, not twisting the tip.
A common feature required for most steerable catheters is a turning means at the proximal end of the catheter. Common turning and turn limiting devices are disclosed by Frisbie et al. U.S. Pat. Nos. 4,664,113 and 4,619,263. These patents disclose screw and thread devices which impart an axial dislocation of a wire employed to steer a catheter.